The use of GaAs on Si technology for the optical interconnection of integrated circuits has been suggested by a number of authors. Such an application would require the use of high-speed LED's with a quasi-planar structure fabricated at selected sites upon the GaAs:Si wafer. These LED's should be capable of operation in excess of 500 MHz.
The typical surface-emitting LED's are the Burrus diode and the mesa diode. A main drawback with the Burrus LED is that it has a larger junction area than its light-emitting area. This tends to introduce a parasitic capacitance which ultimately limits the useful operating speed of the device. With the mesa diode, the junction area is larger than the useful area due to the fact that the electrical contact blocks the light from as much as one third of the junction area. Moreover, the exposed edge of the mesa diode does not allow for making contact with other devices on the same substrate.